foreach(glob("useri/*.txt") as $filename) {
 echo "<li><a href=$filename>$filename</a></li>" ;
}

useri/caca.txt
useri/pipi.txt
useri/pufu.txt
useri/sadzxc.txt
useri/zan.txt

foreach (glob("useri/*.txt") as $filename) {
$file = substr($filename, 6);
 echo "<li><a href=$filename>$file</a></li>" ;
}